Radioactive apparatus



July 2,11946. c. w. wALLH-AUsEN 2,403,316 v RADIoAcTIvE APPARATUS Filed July 14, 1945 Patented July 2, 1946 S PATENT OFFICE I RADIoAcTIvE APPARATUS Clarence W.` Wal-lhausen, Morristown, N. J., as-

signor to United States Radium Corporation, New York, N. Y., a corporation of Delaware Application July 14,1943, sena1No.494,616

This invention is concerned with self-luminous indicators such as clock dials, electrical instru" ment dials, and the like, and provides an improved apparatus having a much longer life than those available heretofore.

It has been customary to produce self-luminous instrument dials by painting thedials with a paint comprising a phosphor, i. e. a phosphorescent material such as zinc sulphide, and a radioactive materialV such asa radium salt which gives off rays that bombard the phosphor and cause it to glow. Dials so constructed are used in a variety of instruments and haverecently found Wider application in airplane instrument dials, especially in Y air-craft adapted for night flying.

It has been found that selffluminous indicator dials fashioned as described above have relatively short useful life, even though the proportion of radioactive material employed is high.y This is believed to be due to the fact that the bombardment of the' phosphor' (e. g. zinc {sulphide) by radium results in deterioration of the phosphor (e. g. sulphide crystal) and the eventual loss of luminosity.v Whatever be the explanation, I have found that the useful life of self-luminous indicator dials, and the like, can be increased many fold if means are provided for interrupting the bombardment of the phosphor by rays, etc., from vthe radioactive material, except rduring times when observations are being made.` By employing a face member, 'such as an indicator dial, having thereon a marker comprising a phosphorescent coating material that is nonradioactive but is capable of being activated by alpha rays, an activator member coated with a nonluminous radio active materialcapable of emitting alpha rays and spaced from but loperatively associated With the face member, and means for interrupting the passage of alpha rays from the activating member to the marker, I4 am able to increase the useful life of the phosphorescent coating matera1 many times. A simple form of apparatus of my` invention comprises a transparent slide, for example a plate of glass which carries markers, for example numbers painted thereon with non-radioactive but responsive zinc sulphide paint.` Back of the glass dial and spaced therefrom a short distance is the activator mem-l ber, which may be a radioactive foil or a lm of coating composition containing a radioactive material. In either case, the activator member is non-luminous, *butv gives off alpha rays which strike the markers on the glass side or dial .and cause thezinc sulphide therein to glow. The glow will continue as long as the alpha rays bombard 5 Claims. (Cl. Z50-72) 2 ,s the zinc sulphide, but bombardment can beJ interrupted in accordance with my inventionby inten. posing between the activator member and the face member, i. e. the glass plate bearing the markers, a sheet of material, for example, a metal slide which is impervious to alpha radiations.A

By interposing the metal slide between the glassy slide and the radioactive film, except whenthe indicator is in use, the life of the face member can be increased many times. 'y

In another form of. the apparatus of my invention, which is herein claimed, the face member, constructed like an lordinaryclock dial, is vof translucent material, with one ormore numbers, or other markers painted on the face thereof with a' Vnon-luminous Y but ray-responsive phosphor, suchqas zinc sulphidepaint, n, The activator. mem-'1 ber in this case is a pointer which rotates aroundk in front of the markers, which conveniently are4 arranged in a circle with the axle of the pointer as I.

a` centers-The pointer carries'a Vradioactive foil or film on its underside 0in theneighborhood. of

the markers. As the pointer rotates, each marker y on the dial is caused to glow consecutively ,v'vhilet theothers remain dark., This type of [structure affords two distinct advantages; The life ofthe phosphorescent material, i. e. the zincsulphide paint is increased because most of the time each marker is beyond the range of rays given offby the radioactive foil or film on the pointer mein',-V ber, and, so does not deteriorate under bombard-- ment. caused to concentrate on only the pertinent ob. servation, i. e. the marker that isilluminated. This reduces fatigue, animportant consideration in night flying and the like.

These and other features of my inventonwill be understood more thoroughly in the light of the following detailed description, taken inconjunction with the `accompanying `drawing,'x'inl which:

Figs. 1 and 2 illustrate one type Yof indicator mechanism constructed in accordance with myY invention;

Figs. 3, 4, 5f and 6` illustrate modified andpre-Y ferred forms of indicators of my invention;v and Fig. 7 illustratesa further form of apparatus of Amy invention in which :the bombardment of Moreover, the eyes of an observerare lz, la, n.15, ls, l1, ls and arranged lin a circle around it's periphery.

v alpha particles and so are on the face of the marker Y1 and immediately over the circle of markers is lplaced a radioactive member 22jsuch as apiece `of Vradioactive foil or a radium lm. The radio- `active foil or lm is spacedfrom the markers, but passes over them when the pointer' is rotated, iso thateach marker successively is Ibombarded lby alpha rays. The pointer is rotated by means, such as a clock-work (not shown).

markers which is beingusefully employed for observation'purposes is activated at the moment. The other markers are outside lthe range of the at rest and unborn- `barded'. j Thev dial constructed inaccordancewith Figs. 1 and 2 will last many times longer thandials `formed by painting the several markers with a fself-luminous paint, for example,.a paint formed :of` zinc sulphide containing a radium active substance, such asradium chloride. y

l Figs. 3, 4, and illustrate three preferred 3modications Yof an indicator. constructedV in accordance with my invention. In allfcases, the aplparatus comprisesa dial or face member,v of transparent ortranslucent material, for example Iglass or plastic. The front face of the dial is masked .witha materialwhich-cuts. off light. Thus, the face ofthe/material, except at.the

lmarkersl, 32, 33, 34, 35, 367/31, 38,1may be Vjcoatedwith blackpaint Yor thelike. The markerv fareas. however, aretransparent or translucent `and-the back of-the dial, at least inthe region of the translucent markers, is covered with-thenon-radioactive butresponsive phosphor 44, for example zinc sulphide paint. Y Asjshownn Figs. 4 and 6, the responsive -phosfphorr- 44- maybeused tocoat only the marker areas themselves. or,` in the case in which Vthe front of` the dialhas been painted vblack except at the markers, the whole back surface of the dial may bepainted with the responsive phosphor,

4 5, as shown in Fig. 5. Y

In the case of the three types illustrated byY Figs. 4, 5' and 6.Y the apparatusisl provided with a pointer which is mountedY behind the' dial and bears an activator 4i of radioactive material, for example, a pieceof radioactive foil prepared as described and( claimed in copending application SerialNoi 407.098, filedAugust 15; 1941, by Alois Fischer. The foil is mounted on the tip of ,the-pointer opposite the circle of markers.

i -As shown in Fig. 4, the pointer may be driven Y by a shaft 42 from inside the apparatus so-that However, as. it rotates, only that portion of the marker or spot 50 will appear on the marker arc between the numerals 5 and I 0.

Naturally enough, the markers on the dial mayV take a great variety of forms and may be placed in a variety of ways.

In the apparatus of Fig. 7, thevactivator member is not movable. In this apparatus, the vface comprises a glass slide 10'von thev underside of which a 4plurality of markers 1|, 12 are provided.

y'Ihese markers are made of non-radioactive but responsive phosphor such as Zinc sulphide paint. The glass slide is mounted in a .case 'I3 of conventional design. The bottom of the case 14 is coated. with a lm of radioactive substance, forV example, a sheet of radioactive copper foil 15.

Alpha rays from the foil cause the 'markers ony the underside ofthe glass slide to glow when the apparatus is in use. When the apparatus is taken f i tion which comprises ar translucent face meml ber, Ya marker mounted on the back of the face member and formed of a non-radioactive but responsive phosphor capable A,of being activated by alpha rays, a pointer spaced from but movable over the rear surface of the face member. in prox- Vimity to theY marker, and a radioactive member of non-luminescent radio-active material which emits alpha rays, said radioactive memberbeing .e mounted on the pointer in such a position that alpha rays therefrom strikethe marker whenthe pointer passes over it. p

2. Ina self-luminousV indicatoni the combination which comprises a translucent face member, Y

a marker mounted on the back ofthe face meme ber and formed of a non-radioactive 'but responsive phosphor capable of being activated by alpha rays,'a mask mountedv on theA front of the face memberto obscure theface except in the neighborhood of the marker,l a. pointer spaced from.. but movable vover the back surface of the face'.

member in proximity'to the marker, aradioactive member of non-luminescent radioactive material which emits alpha rays mounted on the pointer in such a position that alpha rays fromthe member strike the marker when the pointer passes over it. Y

3. In a self-luminous indicator, the combination which comprises a translucent face member, a unitary marker coating affixed on the back of the face member and formed of a non-radioactive i but responsive phosphor capable of being activated by alpha rays, a mask on the front of the face member, said maskY having openingsztherein arranged in an indicator pattern and adapted to permit observation of phosphorescence induced in the marker coating, a pointer spaced from but movable over the surfaceof the. face member in proximity to the marker, and a radioactive activator member of non-luminescentradioactive material which Vemits, alpha rays, the

, activator member lbeing mounted on the pointer i in such a position that alpha rays therefrom Y strike the marker coating when the pointer passes over it. 4. In aself-luminous indicator, the combination which comprises a translucent facemember, a marker mounted on the back of the `face member and formed of a non-radioactive but responsive phosphor capable of being. activated by alpha rays, a1 movable member spaced from and coating the back surface of the face memberl behind each unmasked portion, an Iactivator member mounted adjacent said face member, said face and activator members being relatively movable, and a coating of radio-active material mounted and positioned on said activator member so that said movement causes said radioactive material to pass in activating proximity to said areas of phosphorescent material on the l0 back of said unmasked portions.

CLARENCEl W. WALLHAUSEN. 

